Air dryer reservoir module components

ABSTRACT

An air dryer and reservoir assembly for providing compressed air from an air compressor ( 20 ) on a heavy motor vehicle which includes an air dryer ( 14 ) connected to receive compressed air from the air compressor ( 20 ) and a secondary reservoir ( 12 ), including an integral purge volume ( 34 ), for storing compressed air which passes through the air dryer ( 14 ), with the air dryer ( 14 ) and the secondary reservoir ( 12 ) being securely attached to a housing ( 16 ) to form an air dryer reservoir module ( 10 ). A primary reservoir ( 18 ) for storing compressed air from the air dryer ( 14 ) is located remote from the air dryer reservoir module ( 10 ). A pressure equalizing mechanism ( 57 ) is disposed between the primary reservoir ( 18 ) and the secondary reservoir ( 12 ) for keeping pressure in the two reservoirs ( 12,18 ) equal. Components located within the housing ( 16 ) control air flow between the air dryer ( 14 ) and the primary and secondary reservoirs ( 18,12 ) and also monitor the pneumatic brake system circuits fed by the primary and secondary reservoirs ( 18,12 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/030,583, filed Feb. 25, 1998 now U.S. Pat. No. 6,074,462, which is acontinuation-in-part of U.S. patent application Ser. No. 08/993,931,filed Dec. 18, 1997 now U.S. Patent No. 5,917,139.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to air dryers and more particularly to an airdryer and a reservoir, including a separate purge volume, constructedtogether as a module.

2. Description of Prior Art

Air dryers have been used to dry the air in a heavy vehicle air brakesystem for many years. The advantages of clean and dry air in air brakesystems has long been recognized, as moisture entrained in the air brakesystem may during cold weather operation cause the components of the airbrake system to freeze, thus rendering the system inoperable. Theseprior art air dryers normally include a desiccant material through whichthe compressed air flows. When the vehicle air compressor has chargedthe vehicle air reservoirs to a sufficient pressure level, thecompressor is unloaded so that the compressor no longer compresses air.When the compressor is unloaded, a signal is transmitted to a purgevalve carried within the air dryer which causes stored compressed air tobackflow through the desiccant at a controlled rate to regenerate thedesiccant. The air used to regenerate the desiccant can be either fromcompressed air stored in an integral purge volume within the air dryeror from compressed air stored in a separate reservoir.

Most prior art compressed air systems for heavy vehicle air brakeapplications use three reservoirs which are separate from the air dryer.A compressor feeds compressed air to the air dryer which after flowingthrough the desiccant bed is fed to a remote supply reservoir. Thesupply reservoir is connected to feed compressed air to a primaryreservoir and a secondary reservoir. The primary and secondaryreservoirs feed pneumatic circuits which can control the air brakesystem of the vehicle. For protection from loss of air pressure theprimary and secondary reservoirs each include a check valve in theirpneumatic connections to the supply reservoir. A pneumatic control lineextends from the supply reservoir to an air pressure governor whichcontrols loading and unloading of the air compressor.

SUMMARY OF THE INVENTION

The present invention is for an air dryer and reservoir assembly, forproviding compressed air from an air compressor for operating the brakesof a heavy motor vehicle, which includes an air dryer connected toreceive compressed air from the air compressor, a secondary airreservoir separate from the air dryer, a housing containing pneumaticcircuit components for controlling the flow of compressed air from theair compressor through the air dryer to the secondary reservoir havingthe air dryer securely attached to one section thereof and the secondaryreservoir securely attached to another section thereof for securing theair dryer and the secondary reservoir together as a unitary air dryerreservoir module. The compressed air brake system with the air dryerreservoir module also includes a primary air reservoir having apneumatic connection to the housing disposed remote from the secondaryair reservoir with the housing containing pneumatic circuit componentsfor controlling compressed air flow between the air dryer and theprimary air reservoir. Pneumatic circuit protection valves are disposedwithin the housing for monitoring the pneumatic circuits fed by theprimary and secondary reservoirs. A failure detection means is alsodisposed within the housing for detecting a failure of the pneumaticcircuits which are fed by the primary and secondary reservoirs and inthe event of a failure of these pneumatic circuits the speed of theheavy vehicle is limited.

The herein disclosed air brake system's air charging and treatmentsub-system referred to as the air dryer reservoir module provides for asimplified and cost effective air charging sub-system, using integratedcomponents. The air dryer reservoir module is configured in a way thatallows the elimination of the supply reservoir, which is used in thestandard three reservoir system, while providing a means ofsimultaneously sensing both the primary reservoir and the secondaryreservoir for air compressor and air dryer control.

The air dryer reservoir module integrates components such as pressureprotection valves, the air compressor governor, pressure relief valves,pressure sensors and the like in a way that eliminates the need for thesupply reservoir, the supply reservoir safety valve, several of thestandard three reservoir system's external lines and many of itsfittings. The reduction of components, fittings and pneumatic linesreduces potential failure modes. With respect to a standard threereservoir system, the air dryer reservoir module integrates thefollowing components: air dryer, primary and secondary check valves,supply and secondary drain valves, supply reservoir safety valve, thecompressor governor, auxiliary system pressure protection valves, andthe supply and secondary reservoirs.

A purge volume can be built into the end of the secondary reservoir towhich the air dryer is attached. An internal baffle separates thesecondary reservoir volume from the purge volume. Internal communicationpassages connect the secondary reservoir and purge volume to the airdryer. The dryer reservoir module can also be constructed to equalizethe pressure between the primary reservoir and the secondary reservoir,such that if the vehicle is parked for a given period of time thepressure cannot be replenished. Thereby limiting the use of the vehiclewith a severely leaking reservoir.

BRIEF DESCRIPTION OF DRAWINGS

For a better understanding of the invention reference may be had to thepreferred embodiments exemplary of the inventions shown in theaccompanying drawings in which:

FIG. 1 is an illustration of a prior art three reservoir compressed aircharging system;

FIG. 2 is an illustration of a compressed air charging system using anair dryer reservoir module according to the present invention;

FIG. 2A is an illustration of an inboard view of a portion of thecompressed air charging system using an air dryer reservoir module shownin FIG. 2;

FIG. 3 is a perspective view of an air dryer reservoir module accordingto the present invention;

FIG. 4 is an illustration of an air dryer reservoir module according tothe present invention showing some of its internal pneumatic flow pathsand control components;

FIG. 5 is an illustration of an air dryer reservoir module according tothe present invention used in a service brake system for a heavy motorvehicle;

FIG. 6 is a schematic illustration showing the components included inone embodiment of the air dryer reservoir module; and

FIG. 6A is a view of an air dryer reservoir module that integrates thecomponents shown in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and FIGS. 2 and 3 in particular there isshown an air dryer reservoir module 10 according to the presentinvention. The air dryer module 10 provides compressed air received froman air compressor 20 for operating the brakes of a heavy motor vehicle.The air dryer module 10 includes an air dryer 14 connected to receivecompressed air from the air compressor 20, a secondary air reservoir 12separate from the air dryer 14, and a housing 16 containing pneumaticcircuit components for controlling the flow of compressed air from theair compressor 20 through the air dryer 14 to the secondary reservoir 12and a primary reservoir 18. The housing 16 has the air dryer 14 securelyattached to one section thereof and the secondary reservoir 12 securelyattached to another section thereof for joining the air dryer 14 and thesecondary reservoir 12 together forming the unitary air dryer reservoirmodule 10. The compressed air brake system with the air dryer reservoirmodule 10 also includes the primary air reservoir 18 having a pneumaticconnection 22 to the housing 16 disposed remote from the secondary airreservoir 12. The housing 16 also containing pneumatic circuitcomponents for controlling compressed air flow between the air dryer 14and the primary air reservoir 18. Pneumatic circuit protection valvesare disposed within the housing 16 for monitoring the pneumatic circuitsfed by the primary reservoir 18 and the secondary reservoir 12. Afailure detection means is also disposed within the housing 16 fordetecting a failure of the pneumatic circuits which are fed by theprimary and secondary reservoirs 18,12 and in the event of a failure ofthese pneumatic circuits the speed of the heavy vehicle is limited.

Referring to FIG. 1 there is shown a relatively standard prior art threereservoir pneumatic charging system for the brake system of a heavymotor vehicle. Most prior art compressed air systems for heavy vehicleair brake applications use a primary reservoir 18, a secondary reservoir12 and a supply reservoir 60 which are separate from the air dryer. Acompressor 20 feeds compressed air to an air dryer 62 which afterflowing through the desiccant bed is fed to the remote supply reservoir60. The supply reservoir 60 is connected to feed compressed air to theprimary reservoir 18 and the secondary reservoir 12. The primaryreservoir 18 and the secondary reservoir 12 feed pneumatic circuitswhich can control the air brake system of the vehicle. For protectionfrom loss of air pressure the primary and secondary reservoirs eachinclude a check valve, 66 and 64 respectively, in their pneumaticconnections to the supply reservoir 60. A pneumatic control line 68extends from the supply reservoir 60 to an air pressure governor 70,mounted on the air compressor 20, which controls loading and unloadingof the air compressor 20. The secondary reservoir 12 also has attachedthereto an 85 psi pressure protection valve 72 and a 55 psi pressureprotection valve 74 which feed accessories on the heavy vehicle. Thesupply reservoir 60 includes a safety valve 76 which is set for 150 psi.All three of the reservoirs 12, 18 and 60 include a manual drain valvewhich can be used for draining liquid from their respective reservoir.

Comparing FIGS. 1 and 2 illustrates the difference between the air dryerreservoir module 10 and the standard three reservoir system. The airdryer reservoir module 10 integrates components, eliminates pneumaticlines and connections as compared to a standard three reservoir systemas shown in FIG. 1. The air dryer reservoir module 10 which is one ofthe air brake system's charging sub-systems is intended for use on heavyvehicles, such as tractors and trucks, and is configured as shown in theFIGS. 2 and 3. Manufacturing of the air dryer reservoir module 10 systemis intended to be by conventional methods.

The air dryer reservoir module is different from the prior art in thatit integrates charging system components in a way that eliminatescomponents, pneumatic lines and pneumatic connections thereby reducingfailure modes. The air dryer reservoir module 10 is thought to be thefirst of its kind to utilizes the ABS/EBS brake system ECU tocommunicate system failures to the engine ECU to instruct the engine tolimit vehicle speed. The air dryer reservoir module 10 concepteliminates the supply tank 60 thereby allowing the primary and secondaryservice tanks 12 and 18 to communicate directly with the integrated airdryer 14 through protection valves 35 and 36. This allows the protectionvalves 35, 36 to be integrated into the air dryer module 10, reducingexternal components and pneumatic lines.

Referring now to FIGS. 4 and 5, the air dryer reservoir module 10operates as follows. Charge air from the air compressor 20 enters theair dryer reservoir module 10 at its supply port 31, flows through apurge valve 32 to the desiccant bed 33, fills the purge volume 34, flowsthrough a purge orifice (not shown) and flows out a single check valve(not shown). This represents the same charge cycle as used in anAlliedSignal AD-9 or AD-IP air dryer. From the delivery of the singlecheck valve the charge air flows to the supply of the primary protectionvalve 35 and secondary protection valve 36. Charge air pressure buildsuntil the protection valves 35, 36 open, allowing air to flow to theprimary reservoir 18 and the secondary reservoir 12. Charge air pressurecontinues to build until the pressure sensors 37 or a mechanicalgovernor (not shown) reach cutout pressure. At cutout pressure the threeway solenoid 39 or the mechanical governor opens, sending a controlsignal through compressor unloader port 40, unloading the compressor 20and opening the purge valve 32 purging the air dryer 14. The purge cycleis the same as that of the AlliedSignal AD-9 or AD-IP air dryer. The airdryer reservoir module's 10 integrated component configuration makes itcompatible with both integral purge and system purge type air dryeroperation and both mechanical and electrical type governors. This allowsa single dual function electric solenoid to control the air compressor20 unloading function and to purge the air dryer 14 using both theprimary and secondary service reservoirs 18 and 12 respectively. Thisconfiguration also allows both reservoirs 12, 18 to purge simultaneouslythereby reducing the total system pressure drop required to regeneratethe desiccant bed 33 with system purge type air dryer operation. Use ofpressure protection valves 35 and 36 instead of single check valves 66and 64 reduces compressor 20 cycling. Without the use of check valves 64and 66 primary reservoir 18 and secondary reservoir 12 are common atpressures above the protection valves 35,36 opening pressure. Therefore,pressure differentials do not develop between primary reservoir 18 andsecondary reservoir 12 as air is consumed. Pressure differentials candevelop in standard three reservoir system due to improperly sizedreservoirs and use of accessory systems, causing the compressor to cutinbefore the air pressures in both reservoirs 12, 18 have dropped to thecutin pressure.

The air dryer reservoir module 10 can be designed to utilize servicereservoir air to purge the desiccant, i.e., supply purge. The operationof the air dryer reservoir module 10 in a supply purge mode will besimilar to that of an AlliedSignal AD-SP air dryer. The integralpressure protection valves 35, 36 will eliminate the need for externallyplumbed protection valves. The internal protection valves 35 and 36,when open will allow air to flow back to a special two position threeway system purge solenoid, located where the three way solenoid 39 is inthe integral purge design. The special two position three way systempurge solenoid will be controlled by the BBS ECU with inputs from thepressure sensors 37 through sensor/solenoid I/O 44. The system purgesolenoid will be designed to communicate a control signal to thecompressor 20 unloader and the air dryer purge valve 32 independently.At cutout pressure the system purge solenoid will unload the compressorand open the purge valve 32. The system purge solenoid will then closeonly the purge valve 32 after a predetermined amount of system air isused to purge the dryer's desiccant bed 33. At cutin pressure the systempurge solenoid will then load the compressor 20 starting the cycle over.

Referring now to FIG. 6, the embodiment of the illustrated air dryerreservoir module 10 operates as follows. Charge air from the aircompressor 20 enters the air dryer reservoir module 10 at its supplyport 31, fills the purge volume 34, and flows out a single check valve13. Check valve isolates the primary reservoir 18 and the secondaryreservoir 12 from the output of air dryer 14. An over pressure safetyvalve 21 which is set for 150 psi is disposed at the outlet from airdryer 14. From the delivery of the single check valve 13 the charge airflows to the supply of the primary protection valve 35 and secondaryprotection valve 36. Charge air pressure builds until the protectionvalves 35, 36 open, allowing air to flow to the primary reservoir 18 andthe secondary reservoir 12. Charge air pressure continues to build atthe outlet of check valve 13 until a mechanical governor 15, which isconnected to the outlet of check valve 13, reach cutout pressure. Atcutout pressure, which is set at 130±5 psi, the mechanical governor 15opens, providing a pressure drop signal through line 19, unloading thecompressor 20 and providing a pneumatic signal along line 17 forinitiating purging of the air dryer 14 with the compressed air containedin purge volume 34. Compressor 20 remains unloaded until the pressure togovernor 15 falls below the cutin pressure, which is set at 105 psi. Atthe cutin pressure the governor 15 closes and the compressor is loadedto again supply compressed air to the inlet 31 of air dryer 14.

The primary protection valve 35 is set to open at 103±3 psi and to closeat approximately 95 psi. The secondary protection valve 36 is set toopen at 109±3 psi and to close at approximately 100 psi. When bothprotection valves 35 and 36 are open, the primary reservoir 18 and thesecondary reservoir 12 are in free fluid communication. Secondaryreservoir 12 provides compressed air to a vehicle leveling supply portthrough an accessory protection valve 41 which is set to open at 85±3psi and to close at approximately 72 to 83 psi. Secondary reservoir 12also provides compressed air to vehicle accessories through an accessoryprotection valve 43 which is set to open at 55±3 psi and to close atapproximately 45 to 55 psi.

The air dryer reservoir module 10 is designed to accommodate therequirements of both FMVSS 121 and EEC regulation No. 13. The air dryerreservoir module 10 is also designed to interact with the ABS/EBSsystem's J1939/J1922 engine serial link to allow the limiting of vehiclespeed in the event of a single circuit brake system failure, eitherprimary or secondary. The air dryer reservoir module 10 reduces thenumber of OEM installed charging sub-system components, pneumatic linesand connections as follows: Major charging system components—four forair dryer reservoir module 10 vs. thirteen for a three reservoir system;pneumatic lines—three for air dryer reservoir module 10 vs. six for athree reservoir system; and pneumatic connections—thirteen for air dryerreservoir module 10 vs. thirty two for a three reservoir system.

FIG. 5 shows the air dryer reservoir module in a complete service brakesystem. The air dryer reservoir module 10 system can be designed tocommunicate pneumatic circuit failures through the ABS/EBS ECU 50 to theengine serial link (J1922/J1939) to instruct the engine to go into a“limp” mode. The intention of this feature is to provide a “nuisance”motivator to the operator to have the vehicle repaired. The systemoperates as follows: In the event of a failure of a pneumatic systemwhich is supplied by either the primary reservoir 18 or the secondaryreservoir 12 the air dryer reservoir module's 10 integral pressuresensors 37 communicates the system pressure status to the ABS/EBS ECU50. The ECU 50 instructs the engine control module (ECM) 52 to limitvehicle speed if the vehicle is in excessive of a set limit.

Referring now to FIG. 4 there is shown the secondary reservoir 12 withan integral purge volume 34. A baffle 53 separates the purge volume 34from the secondary reservoir 12. An internal tube 54 extends through thepurge volume 34 to connect the reservoir 12 through connections withinhousing 16 to the air dryer 14. A connection 55 connects the purgevolume 34 through connections within housing 15 to the air dryer 14.This construction eliminates external lines for connecting the air dryer14 to the purge volume 34 and the secondary reservoir 12. External lineshave the potential for leak points, and create customer handling andmounting concerns. Building the purge volume 34 required for the airdryer into the secondary reservoir 12 allows the use of a compact systempurge air dryer desiccant cartridge and this minimizes the spacerequired. Baffle 53 has tube 54 attached through it and the tube 54extends through the purge volume 34 and terminates at the head of thereservoir. The head of the reservoir has attached to it the housing 16which is integral with air dryer 14. The air dryer communicates withboth volumes 12 and 34 via separate passages 54 and 55.

With a leaking reservoir 12 or 18 the dryer reservoir module 10described above will recharge the surviving reservoir indefinitely,thereby holding off the spring brakes. The driver can choose to operatethe vehicle with limited braking efficiency for an unlimited period oftime even though one of the reservoirs does not hold pressure. Inanother embodiment the dryer reservoir module 10 can be constructed toequalize the pressure between the reservoirs 12 and 18, such that if thevehicle is parked for a given period of time the pressure cannot bereplenished thereby limiting the use of the vehicle with a severelyleaking reservoir.

As shown in FIG. 6 and described above, pressure protection valves 35and 36 are used to supply compressed air to the primary reservoir 18 andthe secondary reservoir 12. The pressure protection valves 35, 36 areset to pressurize the primary reservoir 18 first, provided the samepressure exists within the primary and secondary reservoirs. At fullsystem pressure the pressure protection valves 35, 36 are open, insuringequal pressure in both the primary and secondary reservoirs 18 and 12.However, the pressure protection valve opening pressure is dependentupon the downstream reservoir pressure, therefore, if the reservoirpressures are not equal the pressure protection valve which has thehighest downstream pressure will open first. Parking the vehicleovernight or for extended periods of time may cause the primary andsecondary reservoir pressures to become unequal. During recharging ofthe air system the secondary reservoir 12 may charge before the primaryreservoir 18. It may be desirable to limit the duration the vehicle canbe operated in the condition where one reservoir has significantlyreduced pressure. By using a pressure equalizing mechanism, such as aconnecting line with a suitable orifice 57, the pressures in thereservoirs 12 and 18 slowly become equal so that during recharging ofthe air system the primary reservoir 18 will charge first. Furthermore,if the primary reservoir 18 has become ruptured or has a severed leak,again the pressure in both reservoirs 12 and 18 will migrate to 0 psi;however, the primary reservoir 18 can be recharged, but the essentialaccessories and air suspension will not be pressurized because thesecondary reservoir 12 cannot be recharged. The pressure equalizingmechanism 57 will cause the pressure in both reservoirs 12 and 18 to beequal, thereby charging the primary reservoir 18 first and limiting theuse of the vehicle after a severe leak in either the primary orsecondary reservoirs 18 and 12.

1. A method for pressurizing and depressurizing a compressed airreservoir including a purge chamber in fluid communication with an airdryer, a service chamber in fluid communication with the air dryer, anda baffle defining the purge and service chambers, the method comprising:pressurizing the purge chamber with first dried compressed air from theair dryer; pressurizing the service chamber with second dried compressedair from the air dryer without commingling the first dried air and thesecond dried air; and depressurizing the purge chamber to regenerate theair dryer.
 2. The method for pressurizing and depressurizing acompressed air reservoir as set forth in claim 1, further including:depressurizing the service chamber to operate a compressed air system.3. The method for pressurizing and depressurizing a compressed airreservoir as set forth in claim 1, wherein the purge chamber ispressurized before the service chamber.
 4. The method for pressurizingand depressurizing a compressed air reservoir as set forth in claim 1,wherein pressurizing the service chamber includes: controlling a valvebetween the service chamber and the air dryer.
 5. The method forpressurizing and depressurizing a compressed air reservoir as set forthin claim 1, wherein depressurizing the purge chamber includes:transmitting the first dried compressed air from the purge chamber tothe air dryer without commingling the first dried air and the seconddried air.
 6. A compressed air reservoir, comprising: a purge chamber; aservice chamber; a baffle defining the purge and service chambers; afirst passageway for transmitting first dried compressed air between adryer and the purge chamber; and a second passageway for transmittingsecond dried compressed air between the dryer and the service chamber,the second dried compressed air being transmitted between the dryer andthe service chamber without passing through the first passageway.
 7. Thecompressed air reservoir as set forth in claim 6, further including: avalve, which controls passage of the second dried compressed air betweenthe dryer and the service chamber via the second passageway.
 8. Thecompressed air reservoir as set forth in claim 7, wherein the valve is aprotection valve.
 9. The compressed air reservoir as set forth in claim6, wherein the first dried compressed air in the purge chamber istransmitted to the dryer via the first passageway for regenerating adesiccant in the dryer.
 10. The compressed air reservoir as set forth inclaim 9, wherein circuit components cause the first dried compressed airto pass from the dryer to the purge chamber before the second driedcompressed air passes from the dryer to the service chamber.
 11. Thecompressed air reservoir as set forth in claim 6, wherein the secondpassageway is a tube between the dryer and the service chamber.
 12. Thecompressed air reservoir as set forth in claim 11, wherein the tubepasses through the purge chamber.
 13. The compressed air reservoir asset forth in claim 6, wherein a volume of the purge chamber is smallerthan a volume of the service chamber.
 14. A compressed air reservoir,comprising: a purge chamber; a service chamber; a baffle defining thepurge and service chambers; a first passageway for transmitting firstdried compressed air between an air dryer and the purge chamber; and asecond passageway for transmitting second dried compressed air betweenthe dryer and the service chamber, the second dried compressed air beingtransmitted between the dryer and the service chamber without passingthrough the purge chamber.
 15. An air reservoir for use on a motorvehicle, comprising: a first section; a second purge section; a dividerbetween the first and second purge sections; a first connectionconnecting the first section to a source of compressed air; and a secondconnection connecting the second purge section to the source ofcompressed air, the first connection not connecting the first section tothe second purge section and the second connection not connecting thesecond purge section to the first section.
 16. The air reservoir for useon a motor vehicle as set forth in claim 15, wherein the divider createsan air-tight seal between the first and second purge sections.
 17. Theair reservoir for use on a motor vehicle as set forth in claim 15,wherein a volume of the second first section is larger than a volume ofthe first purge section.
 18. The air reservoir for use on a motorvehicle as set forth in claim 15, further including: a valve forcontrolling communication between the second first section and thesource of compressed air.
 19. The air reservoir for use on a motorvehicle as set forth in claim 15, wherein the second first connection isrouted through the first purge section.
 20. The air reservoir for use ona motor vehicle as set forth in claim 19, wherein the second firstconnection is a tube.
 21. The air reservoir for use on a motor vehicleas set forth in claim 15, wherein the first and second connectionsconnect the first and second purge sections, respectively, to the sourceof compressed air via an air dryer.
 22. An air supply system for a motorvehicle brake system, comprising: a compressor for supplying compressedair; an air dryer connected to receive compressed air from the aircompressor, the dryer including a desiccant bed through which thecompressed air flows for providing a dry compressed air source foroperating the brake system; and a reservoir, including: a first section;a second purge section; a baffle defining the first and second purgesections; a first passageway connecting the first section to the sourceof the dry compressed air; and a second passageway connecting the secondpurge section to the source of the dry compressed air, the drycompressed air being transmitted between the source and the second purgesection without passing through the first section.
 23. The air supplysystem for a motor vehicle brake system as set forth in claim 22,further including: a housing having a first section connected to thedryer and a second section connected to the reservoir for joining thedryer and the reservoir as a unitary unit.
 24. The air supply system fora motor vehicle brake system as set forth in claim 22, wherein: a firstportion of the dry compressed air is transmitted between the dryer andthe first section via the first passageway; and a second purge portionof the dry compressed air is transmitted between the dryer and thesecond purge section via the second passageway.
 25. The air supplysystem for a motor vehicle brake system as set forth in claim 24,wherein: the first portion of the dry compressed air is not transmittedto the second purge section; and the second purge portion of the drycompressed air is not transmitted to the first section.
 26. The airsupply system for a motor vehicle brake system as set forth in claim 24,wherein the first portion of the dry compressed air is transmitted fromthe first section to the dryer for regenerating the desiccant bed. 27.The air supply system for a motor vehicle brake system as set forth inclaim 26, wherein the second first portion of the dry compressed air istransmitted to the brake system.
 28. The air supply system for a motorvehicle brake system as set forth in claim 26, wherein circuitcomponents cause the first purge portion of the dry compressed air to betransmitted from the dryer to the first purge section via the firstsecond passageway before the second first portion of the dry compressedair is transmitted from the dryer to the second first section via thesecond first passageway.
 29. The air supply system for a motor vehiclebrake system as set forth in claim 26, wherein a volume of the firstpurge section is smaller than a volume of the second first section. 30.The air supply system for a motor vehicle brake system as set forth inclaim 24, further including: a valve for controlling the transmission ofthe second first portion of the dried compressed air between the dryerand the service chamber first section.
 31. The air supply system for amotor vehicle brake system as set forth in claim 30, wherein the valveis positioned within the second passageway.
 32. The air supply systemfor a motor vehicle brake system as set forth in claim 22, furtherincluding a second reservoir connected to the source of the drycompressed air.
 33. The air supply system for a motor vehicle brakesystem as set forth in claim 22, wherein the air dryer is remote fromthe reservoir.
 34. A reservoir used in combination with an air dryer ina compressed air system, the reservoir comprising: a first chamber forstoring first compressed dried air used for regenerating a desiccantwithin the dryer; a second chamber for storing second compressed driedair for use in a pneumatic system; a baffle between the first and secondchambers; a first passageway for transmitting the first compressed driedair between the dryer and the first chamber, the first compressed driedair not being transmitted to the second chamber; and a second passagewayfor transmitting the second compressed dried air between the dryer andthe second chamber, the second compressed dried air not beingtransmitted to the first chamber.
 35. The reservoir used in combinationwith an air dryer in a compressed air system as set forth in claim 34,further including: a valve for controlling the transmission of thesecond compressed air between the dryer and the second chamber.
 36. Thereservoir used in combination with an air dryer in a compressed airsystem as set forth in claim 35, wherein the valve causes the firstcompressed dried air to be stored in the first chamber before the secondcompressed dried air is stored in the second chamber.
 37. The reservoirused in combination with an air dryer in a compressed air system as setforth in claim 34, wherein the second passageway is a tube passingthrough the baffle.
 38. The reservoir used in combination with an airdryer in a compressed air system as set forth in claim 37, wherein thetube passes through the first chamber.
 39. An air reservoir for use on amotor vehicle, comprising: a first section in independent fluidcommunication with a source of compressed air; a second purge section inindependent fluid communication with the source of compressed air; and adivider between the first and second purge sections.
 40. The airreservoir as set forth in claim 39, wherein the first section is not inindependent fluid communication with the second purge section.
 41. Anair reservoir for use on a motor vehicle, comprising: a first section; asecond purge section; a divider between the first and second purgesections; a first passageway independently fluidly connecting the firstsection to a source of compressed air; and a second passagewayindependently fluidly connecting the second purge section to the sourceof compressed air, the first passageway not independently fluidlyconnecting the first section to the second purge section and the secondpassageway not independently fluidly connecting the second purge sectionto the first section.
 42. The air reservoir for use on a motor vehicleas set forth in claim 41, further including: a valve for controlling thefluid communication between the second first section and the source ofcompressed air via the second first passageway.
 43. The air reservoirfor use on a motor vehicle as set forth in claim 41, wherein the secondfirst passageway is passes through the first purge section.
 44. The airreservoir for use on a motor vehicle as set forth in claim 43, whereinthe second first passageway is a tube.
 45. An air supply system for amotor vehicle brake system, comprising: a compressor for supplyingcompressed air; an air dryer connected to receive compressed air fromthe air compressor, the dryer including a desiccant bed through whichthe compressed air flows for providing a dry compressed air source foroperating the brake system; and a reservoir, including: a first section;a second section; a baffle defining the first and second sections; afirst passageway connecting the first section to the source of the drycompressed air; and a second passageway connecting the second section tothe source of the dry compressed air, the dry compressed air beingtransmitted between the source and the second section without passingthrough the first section during a first operating mode.
 46. The airsupply system as set forth in claim 45, wherein, during the firstoperating mode, a first portion of the compressed air is stored in thefirst section before a second portion of the compressed air is stored inthe second section.
 47. The air supply system as set forth in claim 46,wherein the second portion of the dry compressed air is transmitted fromthe first section to the second section during a second operating mode.48. The air supply system as set forth in claim 47, wherein the firstportion of the dry compressed air is transmitted from the first sectionto the dryer for regenerating the desiccant bed during the firstoperating mode.
 49. The air reservoir for use on a motor vehicle as setforth in claim 15, wherein the first section is a service section. 50.The air supply system for a motor vehicle brake system as set forth inclaim 22, wherein the first section is a service section.
 51. The airreservoir as set forth in claim 39, wherein the first section is aservice section.
 52. The air reservoir for use on a motor vehicle as setforth in claim 41, wherein the first section is a service section. 53.The air supply system as set forth in claim 45, wherein the firstsection is a service section.